JP3571447B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus having an automatic density adjustment function for controlling image forming conditions in accordance with the density of a document.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus having an automatic density adjustment function in recent years has been known in which an image forming condition, for example, a developing bias voltage is controlled in accordance with an original density so as to eliminate fogging of a background portion. . In this apparatus, before each image forming operation, a part or the whole area of this document is detected by document density detecting means, for example, a light amount sensor, and based on the detection result, a preset optimal setting is made. Image forming conditions such as an exposure lamp voltage and a developing bias voltage are controlled.
[0003]
In this case, in order to detect the density of the document as quickly as possible, there is an example in which the density of a part of the document is detected and used as a representative value of the entire document. Further, in this case, the density and area cannot be specified depending on the document, so that a wide range is detected as much as possible. Further, there is an example in which a plurality of original density detecting sensors are arranged in order to detect a wide range without lowering the copy speed.
[0004]
[Problems to be solved by the invention]
However, in the above conventional example, in a case where a part of the document is detected and set as a representative value of the entire document, a detection error increases. In addition, when a wide range is to be detected as much as possible, the detection time becomes longer and the copy speed decreases as the detection range becomes wider. Furthermore, in an example in which a plurality of document density detecting sensors are arranged, there is a disadvantage that the cost increases.
[0005]
The present invention solves such problems in the conventional technology, and can detect a wide range of document densities in a short time without providing a special document density sensor, thereby enabling highly accurate automatic density adjustment. An image forming apparatus is provided.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided an automatic document feeder for automatically feeding a document onto a contact glass, and a document for detecting the density of the document before or during an image forming operation. Density detecting means, image forming condition changing means for changing image density to change image forming conditions, and control means for controlling the image forming condition changing means based on a detection result detected by the document density detecting means And an exposure unit for exposing the original on the contact glass, wherein the automatic original feeding unit detects the presence or absence of an original to be fed, and the temperature of the exposure unit is detected. Exposure section temperature detection means, and based on a detection result by the document detection means, the control means sets the exposure means directly below the contact glass during document feeding by the automatic document feeding means. Arranged at a predetermined position, perform one of the controls in a first document density detecting operation for exposing the document and a second document density detecting operation for exposing the document on the contact glass by moving the exposure means, When the temperature detected by the exposure unit temperature detection means exceeds a set value, the control means controls the second document density detection operation .
[0007]
According to a second aspect of the present invention, when the automatic document feeder detects a document, the controller controls the first document density detection operation .
[0011]
The image forming apparatus according to the first aspect of the present invention detects the document density by exposing the document while the exposure unit is arranged at a predetermined position immediately below the contact glass during the automatic document feeding operation. Therefore, a wide range of document density can be detected in a short time without providing a special document density sensor, and automatic density adjustment with high accuracy can be performed.
[0012]
Further, in the image forming apparatus according to the first aspect, when the document detecting means of the automatic document feeding means detects the presence of the document, the exposing means moves to scan the document on the contact glass. Control is performed to switch from the document density detection operation to a second document density detection operation in which the exposure unit is arranged at a predetermined position immediately below the contact glass during automatic document feeding and the document is exposed. Therefore, an original density detection operation suitable for the arrangement state of the original is performed, and high-precision automatic density adjustment can be performed in a short time and in a wide range as much as possible.
[0013]
Further, in the image forming apparatus according to the first aspect, when the exposure device exceeds a predetermined temperature, the exposure device is disposed at a predetermined position immediately below the contact glass during automatic document feeding, and a second process for exposing the document is performed. Since the control for switching from the document density detecting operation to the first document density detecting operation for moving the exposure means to scan the document on the contact glass is performed, the lighting time of the exposure lamp is shortened. Temperature rise is suppressed, and a decrease in the life of the exposure lamp is prevented. Further, adverse effects on surrounding members and the like are prevented, and the operation of automatic density adjustment is continued.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the image forming apparatus of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a side view showing a configuration of an embodiment of the image forming apparatus of the present invention, and FIG. 2 is a block diagram showing a configuration of a control system. 1 and FIG. 2, this embodiment includes a photosensitive member 1 on which an electrostatic latent image is formed, a charging device 2 for uniformly charging the photosensitive member 1, and a non-image area of the photosensitive member 1. It has an eraser 3 for removing electricity and a developing device 5 for developing a toner image of a copied image.
[0015]
Further, there are provided a transfer belt section 7 for conveying the copy paper at a constant speed, a cleaning unit 8 for collecting the toner remaining on the photoconductor 1 after the transfer, and a static elimination lamp 9 for erasing the residual potential on the photoconductor 1. ing. The contact glass 10 includes a contact glass 10 on which the document 13 is arranged, and an exposure lamp 11 that exposes the document 13 on the contact glass 10. Further, first, second, third, fourth, fifth, and sixth reflected light mirrors 12a, 12b, 12c, 12d, 12e, and 12f for reflecting the reading light of the document 13 and the contact glass 10 are automatically placed. And a lens 14 for forming an image of the reading light of the original 13 on the photoreceptor 1.
[0016]
An exposure device 15 having an exposure lamp 11, a temperature sensor and a first reflected light mirror 12a; an automatic document feeder 16 for automatically feeding the document 13; and a document presence detection sensor for detecting the presence of the document 13. 17 and a document density sensor 18 for detecting a document density from the reflected light from the third reflected light mirror 12c.
[0017]
Further, a temperature sensor 19 for detecting the temperature in the exposure device 15, a main control unit 24 for controlling each unit based on the document density detected by the document density sensor 18, and an exposure device 15 connected to the main control unit 24. And an exposure control unit 25 for controlling the exposure. Further, it has a development control unit 26 connected to the main control unit 24 to control the developing device 5, and a charging control unit 27 connected to the main control unit 24 to control the charging device 2.
[0018]
Next, the operation of this embodiment will be described.
FIG. 3 is a side view showing the operation state of the automatic document feeder, and FIG. 4 is a perspective view for explaining the operation when scanning a document.
[0019]
1 to 4, the photoconductor 1 rotates in the direction of the arrow in the figure, and is uniformly charged by the charging device 2 operated under the control of the main control unit 24 and the charging control unit 27. An exposure device 15 operated under the control of a main controller 24 and an exposure controller 25 moves and scans and exposes the original 13 on the contact glass 10, and first to sixth reflected light mirrors 12 a to 12 f and a lens 14. Is irradiated onto the photoreceptor 1 to form an electrostatic latent image.
[0020]
Next, the non-image area of the photoreceptor 1 is neutralized by the eraser 3, and the developing device 5 operated under the control of the main control section 24 and the development control section 26 develops the electrostatic latent image section with toner. Process. Further, the transfer sheet onto which the toner image has been transferred through the transfer belt unit 7 is discharged after the fixing process. On the other hand, the toner remaining on the photoconductor 1 after the transfer is collected by the cleaning unit 8, and the residual potential on the photoconductor 1 is erased by the discharging lamp 9.
[0021]
Next, an automatic density adjustment method will be described.
In the automatic document feeder 16 provided in the upper part of the main body shown in FIG. 3, after pressing a copy button (not shown) connected to the main control unit 24 and the like, the exposure device 15 moves to move the contact glass 10 before scanning the document. The exposure lamp 11 in the exposure device 15 is turned on under the control of the main control unit 24 and the exposure control unit 25 by moving to the leading end of the document immediately below and stopping.
[0022]
Next, as shown in FIG. 4, the document 13 fed from the automatic document feeder 16 moves on the exposure lamp 11, and the exposure lamp 11 scans the document 13. At this time, the reflected light from the document 13 is received by the document density sensor 18 via the first to third mirrors 12a to 12c of the optical system as shown in FIGS.
[0023]
The detection signal from the document density sensor 18 is input to the main control unit 24 shown in FIG. A developing bias voltage that does not cause background fogging when the background portion of the document 13 is developed, that is, the brightest portion in the document density where the detection level of the document density sensor 18 is large, is set to a predetermined document density. The main control unit 24 calculates the correlation between the output signal of the density sensor 18 and the developing bias voltage, and determines the developing bias voltage to be used in the developing process under the control of the developing control unit 26. Although the developing bias voltage is controlled in accordance with the detected document density here, the applied voltage of the exposure lamp 11 and the charging grid voltage may be controlled.
[0024]
When the density detection from the leading edge to the trailing edge of the document 13 is completed, the document 13 is placed at a predetermined position on the contact glass 10. Next, the exposure lamp 11 of the exposure device 15 starts moving in the lit state to scan the document 13. At this time, the reflected light from the document 13 is irradiated on the photoconductor 1 through the first to sixth mirrors 12a to 12f of the optical system and the lens 14 to form a latent image thereof.
[0025]
Next, switching of the document density detection method will be described.
This automatic density adjustment method is performed under the control of the main control unit 24, and includes two types of first and second document density detection operations. The first document density detection operation is performed by exposing the document 13 to the document 13 at a predetermined position directly below the contact glass 10 under the control of the exposure control unit 25 during automatic document feeding by the automatic document feeder 16. , To detect the original density.
[0026]
The second document density detecting operation is to detect the document density when scanning the document 13 on the contact glass 10 by moving the exposure device 15, and the main control unit 24 performs the first or second document density detection. One of the document density detection operations is selected based on the following detection results (a) and (b), and the control operation is performed.
[0027]
(A) When the document 13 is directly placed on the contact glass 10 without using the automatic document feeder 16, the document presence / absence detection sensor 17 installed near the entrance of the automatic document feeder 16 sets “No Document”. Is detected, and the main control unit 24 recognizes this "no original". In this case, the main controller 24 detects the original density in the second original density detection operation. When the document 13 is placed in the automatic document feeder 16, a document presence / absence detection sensor 17 installed near the document entrance of the automatic document feeder 16 detects “document present”, and detects this “document present”. The main control unit 24 recognizes. In this case, the main controller 24 identifies the original density in the first original density detection operation.
[0028]
(B) When the automatic document feeder 16 is used, the exposure device 15 exposes the document 13 at a predetermined position directly below the contact glass 10 during the automatic document feed as described in (a) above. Detect concentration. That is, the detection is performed by the former first document density detection operation. In this case, since the exposure lamp 11 is turned on during the document density detection and during the subsequent document scanning by the exposure device 15, the small size is used. The exposure lamp 11 continues to be turned on even for the original document. If this operation is continued for a long time, the temperature of the exposure lamp 11 rises and its life is shortened. Further, the rise in the temperature of the exposure device 15 causes the deflection of the resin original scale 20 shown in FIG.
[0029]
For this reason, when the detection result of the temperature sensor 19 installed in the exposure device 15 becomes, for example, 80 ° C. or higher, the main control unit 24 that has taken in the detected temperature moves the exposure device 15 to the second To the original density detection operation. That is, the exposure device 15 is moved to scan the original 13 on the contact glass 10. As a result, except when the document 13 is scanned by the exposure device 15, the exposure lamp 11 is turned off. As a result, the temperature rise of the exposure device 15 is suppressed, and the resin document scale 20 shown in FIG. The accompanying various inconveniences do not occur.
[0030]
【The invention's effect】
As is apparent from the above description, according to the image forming apparatus of the first aspect, the document density is detected in a state where the exposure unit is arranged at a predetermined position immediately below the contact glass during the automatic document feeding operation. Therefore, a wide range of document density can be detected in a short time without providing a special document density sensor, and highly accurate automatic density adjustment can be performed.
[0031]
Further , according to the image forming apparatus of the present invention, when detecting the presence of a document, the exposure means moves from scanning the document on the contact glass to contacting the exposure means during automatic document feeding. Since the document is switched so that it is placed at a predetermined position directly below the glass and the document is exposed, the document density detection operation that matches the document placement state is performed, and highly accurate automatic density adjustment can be performed in the shortest possible time and over a wide range. Will be able to do it.
[0032]
According to the image forming apparatus of the first aspect , when the exposure unit exceeds a predetermined temperature, the exposure unit is arranged at a predetermined position immediately below the contact glass during automatic document feeding to expose the original. From, since the exposure means is switched to scan the original on the contact glass by scanning, the lighting time of the exposure lamp is shortened, the temperature rise of the exposure means is suppressed, and the life of the exposure lamp is prevented from being shortened. In addition, adverse effects on surrounding members and the like are prevented, and the operation of automatic density adjustment can be continued.
[Brief description of the drawings]
FIG. 1 is a side view illustrating a configuration of an embodiment of an image forming apparatus of the present invention.
FIG. 2 is a block diagram showing a configuration of a control system in the embodiment.
FIG. 3 is a side view illustrating an operation of the automatic document feeder according to the embodiment.
FIG. 4 is a perspective view for explaining an original scanning operation in the embodiment.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 photoconductor 2 charging device 3 eraser 5 developing device 7 transfer belt unit 8 cleaning unit 9 static elimination lamp 10 contact glass 11 exposure lamps 12a to 12f first to sixth reflected light mirrors 13 document 15 exposure device 16 automatic document feeder 17 Document detection sensor 18 Document density sensor 19 Temperature sensor 24 Main control unit 25 Exposure control unit 26 Development control unit 27 Charging control unit

Claims (2)

An automatic document feeder for automatically feeding a document onto the contact glass;
Document density detecting means for detecting the density of the document before or during the image forming operation , image forming condition changing means for changing the image density to change the image forming condition, and the document density detecting means A control unit that controls the image forming condition changing unit based on the detected detection result, and an image forming apparatus that includes an exposure unit that exposes a document on the contact glass .
Document detection means for detecting the presence or absence of a document to be fed by the automatic document feeding means;
Exposure unit temperature detection means for detecting the temperature of the exposure means,
Based on the detection result by the document detecting means, the control means arranges the exposing means at a predetermined position immediately below the contact glass during document feeding by the automatic document feeding means, and exposes a document. Perform one of the control in the document density detection operation and the second document density detection operation of exposing the document on the contact glass by moving the exposure unit,
An image forming apparatus , wherein when the temperature detected by the exposure unit temperature detection means exceeds a set value, the control means controls a second document density detection operation . 2. The image forming apparatus according to claim 1 , wherein when the automatic document feeder detects a document, the control unit controls a first document density detection operation .

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